Variable resistance memory device including phase change area defined by spacers

ABSTRACT

A variable resistance memory device and a method of manufacturing the same are provided. The variable resistance memory device includes a multi-layered insulating layer including a plurality of holes formed on a semiconductor substrate, a lower electrode formed in a bottom of each of the holes, a first spacer formed on the lower electrode and a sidewall of each of the holes, a second spacer formed on an upper sidewall of the first spacer, a third spacer formed on a lower sidewall of the first spacer below the second spacer, a variable resistance part that is formed on the lower electrode has a height lower than a height of a top of each hole, and an upper electrode formed on the variable resistance part to be buried in each hole.

CROSS-REFERENCES TO RELATED APPLICATION

This application is a division of U.S. patent application Ser. No. 14/044,367 filed on Oct. 2, 2013, which claims priority under 35 U.S.C. 119(a) to Korean application number 10-2013-0081559, filed on Jul. 11, 2013, in the Korean Patent Office. The disclosure of each of the foregoing application is incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Technical Field

Various embodiments of the inventive concept relate to a nonvolatile memory device, and more particularity, to a variable resistance memory device and a method of manufacturing the same.

2. Related Art

In recent years, with demands on semiconductor devices with high performance and low power, next generation semiconductor memory devices with non-volatility and non-refresh have been researched. As one of the next-generation semiconductor memory devices, variable resistance memory devices are suggested. Examples of the variable resistance memory devices includes random access memory devices (PCRAMs), resistive RAMs (ReRAMs), magnetic RAMs (MRAMs), spin-transfer torque magnetoresistive RAMs (STTMRAMs), and polymer RAMs (PoRAMs).

The variable resistance memory devices perform a memory operation to have a set state or a reset state by controlling a phase-change material, which constitutes a data storage unit, to a crystalline state or an amorphous state.

Attempts to reduce a reset current, that is, a current required to switch a phase-change material to an amorphous state in PCRAMs have been made. Reduction in the reset current of the PCRAMs may be determined by a resistance of the phase-change material layer and a contact area between a lower electrode and the data storage unit.

Thus, at present, attempts to reduce the contact area between the lower electrode and the data storage unit, which may be controlled by a process, have been made increasingly.

SUMMARY

In an embodiments are provided to a variable resistance memory device capable of reducing a reset current, and a method of manufacturing the same.

According to one aspect of an exemplary embodiment, there is provided a variable resistance memory device. The variable resistance memory device may include a multi-layered insulating layer including a plurality of holes formed on a semiconductor substrate, a lower electrode formed in a bottom of each of the holes, a first spacer formed on the lower electrode and a sidewall of each of the holes, a second spacer formed on an upper sidewall of the first spacer, a third spacer formed on a lower sidewall of the first spacer below the second spacer, a variable resistance part that is formed on the lower electrode has a height lower than a height of a top of each hole, and an upper electrode formed on the variable resistance part to be buried in each hole.

According to an aspect of an exemplary embodiment, there is provided a method of manufacturing a variable resistance memory device. The method may include forming a multi-layered insulating layer on a semiconductor substrate, forming a hole exposing a portion of an upper surface of the semiconductor substrate by etching the multi-layered insulating layer, forming a lower electrode in a bottom of the hole, forming a first spacer on the lower electrode and a sidewall of the hole, forming a second spacer on an upper sidewall of the first spacer, forming a third spacer on a lower sidewall of the first spacer, forming a variable resistance part in the hole to have a height lower than that of the hole, and forming an upper electrode on the variable resistance part to be buried in the hole.

According to an aspect of an exemplary embodiment, there is provided a method of manufacturing a variable resistance memory device. The method may include forming a multi-layered insulating layer on a semiconductor substrate, forming a hole exposing a portion of an upper surface of the semiconductor substrate by etching the multi-layered insulating layer, forming a lower electrode in a bottom of the hole, forming a first spacer on the lower electrode and a sidewall of the hole, forming a second spacer protruded from an upper sidewall of the first spacer, depositing a third spacer material into the hole, forming a third spacer on a lower sidewall of the first spacer and below the second spacer by selectively etching the third spacer material, forming a variable resistance part in the hole to have a height lower than that of the hole.

These and other features, aspects, and embodiments are described below in the section entitled “DETAILED DESCRIPTION”.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and other advantages of the subject matter of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIGS. 1 to 8 are views illustrating a method of manufacturing a variable resistance memory device according to an embodiment of the inventive concept.

DETAILED DESCRIPTION

Hereinafter, exemplary embodiments will be described in greater detail with reference to the accompanying drawings.

Exemplary embodiments are described herein with reference to cross-sectional illustrations that are schematic illustrations of exemplary embodiments (and intermediate structures). As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, exemplary embodiments should not be construed as limited to the particular shapes of regions illustrated herein but may be to include deviations in shapes that result, for example, from manufacturing. In the drawings, lengths and sizes of layers and regions may be exaggerated for clarity. Like reference numerals in the drawings denote like elements. It is also understood that when a layer is referred to as being “on” another layer or substrate, it can be directly on the other or substrate, or intervening layers may also be present. In addition, a singular form may include a plural form as long as it is not specifically mentioned in a sentence.

As illustrated in FIG. 1, an insulating layer 120 is formed on a semiconductor substrate 110, and a hole H is formed in the insulating layer 120. A conductive material is gap-filled in the hole H, and recessed using a Cl⁻ or F⁻-based etching gas to form a lower electrode 130 having a certain height in a bottom of the hole H. In the embodiment, although not shown, the semiconductor substrate 110 may include a word line and a switching device. In the embodiment, the insulating layer 120 may be a multi-layered insulating layer including a nitride layer 121 formed on the semiconductor substrate 110, an oxide layer 122 formed on the nitride layer 121, a buffer nitride layer 123 formed on the oxide layer 122, and a buffer oxide layer 124 formed on the buffer nitride layer 123.

As illustrated in FIG. 2, a polysilicon material is deposited to be buried in the hole H in which the lower electrode 130 is formed, and then the polysilicon material is etched back to remain only on a sidewall of the hole H to form a first spacer 140. At this time, the etch back process may be performed using HBr gas, which may prevent the lower electrode 130 from being lost. A nitride layer is deposited to be buried in the hole H in which the first spacer 140 is formed and then recessed to form a sacrificial layer 145 having a certain height on the lower electrode 130. The sacrificial layer 145 may be formed through a wet etch method.

As illustrated in FIG. 3, the first spacer 140 formed on the sidewall of the hole H is selectively oxidized to form a second spacer 150 on a sidewall of the first spacer 140.

As illustrated in FIG. 4, the sacrificial layer 145 formed in the hole H is removed.

As illustrated in FIG. 5, a third spacer material 60 a is deposited in the hole H. The third spacer material 160 a may be nitride. The third spacer material 160 a has a form protruding toward the center of the hole H, and thus the third spacer material 160 a may not be easily buried. Therefore, the third spacer material 160 a is formed in a state in which the third spacer material 160 a is not completely buried in the hole H and a key hole pattern KH is formed in the hole H. The key hole pattern KH is generated by a physical shape of the hole H, and a size of the key hole pattern KH may be controlled according to a degree of protrusion of the second spacer 150, that is, according to a width of oxidation of the first spacer 140.

As illustrated in FIG. 6, only the third spacer material 160 a is selectively etched to form a third spacer 160 on the lower electrode 130 and below the second spacer 150. At this time, the etching of the third spacer material 160 a may be performed using a combination of CH₃F gas and O₂ gas.

As illustrated in FIG. 7, a variable resistance material is deposited to be buried in the hole H. The variable resistance material 170 may be recessed to have a certain height, and thus a variable resistance part 170 having a height lower than that of the hole H may be formed. The variable resistance part 170 may include a phase-change material of which a resistance is changed depending on a crystalline state or an amorphous state according to a temperature, for example, Ge₂Sb₂Te₅ (GST).

As illustrated in FIG. 8, an upper electrode material is deposited to be buried in the hole H, and then planarized to form an upper electrode 180. In the planarization process, the buffer nitride layer 123 among the insulating layer 120 may serve as an etching stopper layer to allow a height of a variable resistance cell to be maintained.

As described above, in the variable resistance memory device according to an embodiment of the inventive concept, since the lower electrode 130 and the variable resistance part 170 are in contact with each other through the key hole KH, a contact area may be reduced, and thus a reset current may be reduced.

The above embodiment of the present invention is illustrative and not limitative. Various alternatives and equivalents are possible. The invention is not limited by the embodiment described herein. Nor is the invention limited to any specific type of semiconductor device. Other additions, subtractions, or modifications are obvious in view of the present disclosure and are intended to fall within the scope of the appended claims. 

What is claimed is:
 1. A variable resistance memory device, comprising: a multi-layered insulating layer including a plurality of holes formed on a semiconductor substrate; a lower electrode formed in a bottom of each of the holes; a first spacer formed on the lower electrode and a sidewall of each of the holes; a second spacer formed on an upper sidewall of the first spacer to a predetermined height; a third spacer formed on a lower sidewall of the first spacer below the second spacer; a variable resistance part formed on the lower electrode and having a height lower than a height of a top of each hole; and an upper electrode formed on the variable resistance part to be buried in each hole, wherein a resistivity of the variable resistance part is changed according to a phase-change of the variable resistance part.
 2. The variable resistance memory device of claim 1, wherein the multi-layered insulating layer includes: a first insulating layer formed on the lower electrode and formed of nitride; a second insulating layer formed on the first insulating layer and formed of oxide; a third insulating layer fainted on the second insulating layer and formed of the nitride; and a fourth insulating layer formed on the third insulating layer and formed of the oxide.
 3. The variable resistance memory device of claim 2, wherein the second spacer is formed through selectively oxidizing the first spacer.
 4. The variable resistance memory device of claim 3, wherein the first spacer, the second spacer, and the third spacer are formed of materials having different etch selectivities from each other.
 5. The variable resistance memory device of claim 4, wherein a height of the variable resistance part is higher than that of the third spacer.
 6. A variable resistance memory device, comprising: a insulating layer including a hole formed on a semiconductor substrate; a lower electrode formed in the hole, the lower electrode having a height lower than that of the hole; a first spacer formed on the lower electrode and a whole sidewall of the hole; a second spacer formed on an upper sidewall of the first spacer to a predetermined height; a third spacer formed on a lower sidewall of the first spacer below the second spacer, an upper surface of the third spacer being contacted with a lower surface of the second spacer and the third spacer including an etching selectivity being different from that of the second spacer; a variable resistance part formed on the lower electrode in the hole; and an upper electrode formed on the variable resistance part in the hole.
 7. The variable resistance memory device of claim 6, wherein the insulating layer includes: a first insulating layer formed on the lower electrode and formed of a nitride material; a second insulating layer formed on the first insulating layer and formed of an oxide material; and a third insulating layer formed on the second insulating layer and formed of the nitride material.
 8. The variable resistance memory device of claim 6, wherein the first spacer includes a poly silicon material.
 9. The variable resistance memory device of claim 8, wherein the second spacer includes a silicon oxide material obtained by oxidizing the first spacer.
 10. The variable resistance memory device of claim 9, wherein the third spacer includes a nitride material. 